linux-kernel - Re: [PATCH] usbvision: remove (broken) image format conversion

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Date:	Tue, 26 Apr 2011 13:54:53 +0200
From:	Hans de Goede <hdegoede@...hat.com>
To:	Ondrej Zary <linux@...nbow-software.org>
CC:	Hans Verkuil <hverkuil@...all.nl>,
	Joerg Heckenbach <joerg@...kenbach-aw.de>,
	Dwaine Garden <dwainegarden@...ers.com>,
	linux-media@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usbvision: remove (broken) image format conversion

Hi,

On 04/26/2011 10:30 AM, Ondrej Zary wrote:
> On Tuesday 26 April 2011, you wrote:
>> On Monday, April 25, 2011 23:23:17 Ondrej Zary wrote:
>>> The YVU420 and YUV422P formats are broken and cause kernel panic on use.
>>> (YVU420 does not work and sometimes causes "unable to handle paging
>>> request" panic, YUV422P always causes "NULL pointer dereference").
>>>
>>> As V4L2 spec says that drivers shouldn't do any in-kernel image format
>>> conversion, remove it completely (except YUYV).
>>
>> What really should happen is that the conversion is moved to libv4lconvert.
>> I've never had the time to tackle that, but it would improve this driver a
>> lot.
>
> Depending on isoc_mode module parameter, the device uses different image
> formats: YUV 4:2:2 interleaved, YUV 4:2:0 planar or compressed format.
>
> Maybe the parameter should go away and these three formats exposed to
> userspace?

That sounds right,

> Hopefully the non-compressed formats could be used directly
> without any conversion. But the compressed format (with new V4L2_PIX_FMT_
> assigned?) should be preferred (as it provides much higher frame rates). The
> code moved into libv4lconvert would decompress the format and convert into
> something standard (YUV420?).

Correct.

>
>> Would you perhaps be interested in doing that work?
>
> I can try it. But the hardware isn't mine so my time is limited.
>

If you could give it a shot that would be great. I've some hardware to
test this with (although I've never actually tested that hardware), so
I can hopefully pick things up if you cannot finish things before you
need to return the hardware.

Thanks & Regards,

Hans
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